Plasmatron-catalyst system

ABSTRACT

A plasmatron-catalyst system. The system generates hydrogen-rich gas and comprises a plasmatron and at least one catalyst for receiving an output from the plasmatron to produce hydrogen-rich gas. In a preferred embodiment, the plasmatron receives as an input air, fuel and water/steam for use in the reforming process. The system increases the hydrogen yield and decreases the amount of carbon monoxide.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 09/182,537 filed Oct. 29, 1998 for “Plasmatron-CatalystSystem”, the teachings of which are hereby incorporated by reference.

[0002] This invention was made with government support under ContractNumber DE-FG07-98ID13601 awarded by the U.S. Department of Energy. Thegovernment has certain rights in the invention.

FIELD OF THE INVENTION

[0003] This invention relates to a plasmatron-catalyst system which canmaximize hydrogen yield and decrease the amount of carbon monoxide.

BACKGROUND OF THE INVENTION

[0004] The pending U.S. application mentioned above, of which thisapplication is a continuation-in-part, discloses and claims the use of arapid response plasmatron for converting hydrocarbon fuels intohydrogen-rich gases. This process may be carried on-board vehicles.

[0005] Converting hydrocarbon fuels into hydrogen-rich gas (reforming)can be achieved with a plasmatron reactor. There are many advantages ofusing a plasmatron in the reforming process. Advantages include fastresponse (less than one second), adequate conversion into hydrogen-richfuel, compactness (high hydrogen productivity), robustness (stableprocess), and the ability of the plasmatron to use many fuels, includinghard-to-reform gasoline, diesel and biofuels.

[0006] For internal combustion applications, the hydrogen purity is notof great importance. High conversion efficiency into hydrogen is notnecessary, since the low weight hydrocarbons that accompany the hydrogenproduced by the plasmatron are also good fuels for use in internalcombustion engines. More important is to minimize the energy consumed inthe plasmatron during the reforming process.

[0007] U.S. Pat. Nos. 5,425,332 and 5,437,250 discloseplasmatron-internal combustion engine systems and the teachings of thesetwo patents are incorporated herein by reference. Plasmatrons of thetype used in the present invention are described in detail in these twopatents.

[0008] Partial oxidation is a preferred method of reforming. Anadvantage of partial oxidation is that it eliminates the need forstoring additional liquids on-board vehicles. Also, a fraction of thefuel is reformed in order to allow the introduction into the cylinder ofan engine hydrogen-rich gas to improve the combustion process. Since theintention of the prior art is not to reform all of the fuel, the issuesof efficiency, although still relevant, have not heretofore driven thedesign of a plasmatron system.

[0009] The previous application discloses the use of plasma catalysison-board vehicles. The process of converting the hydrocarbon intohydrogen rich gases by the use of plasma catalysis addresses mainly theenergy requirement in the plasmatron in the reformation process. Plasmacatalysis, as used for applications in internal combustion engines, candecrease the electrical energy requirement. The prior art does notsuggest the use of catalysts to maximize hydrogen yield nor to decreasethe amount of CO (carbon monoxide) that is produced in the partialoxidation process (The hydrogen yield is defined as the ratio of thehydrogen in the reformats to the amount of hydrogen content in thefuel).

[0010] The prior art does not extend plasma catalysis into the contextof fuel cell vehicles and stationary fuel cells in which very highhydrogen yields and low energy consumption are required.

[0011] The requirements on a reformate for fuel cell applications arevery different from those for use of hydrogen rich gas in internalcombustion engines. As described above, for application to internalcombustion engines, it is not necessary to have high yields, a veryefficient process or very clean gas. As used herein, clean gas isdefined to be gas with small concentrations of CO, since CO is a poisonto some types of fuel cells that are presently being considered for bothstationary and vehicular applications, of which the PEM fuel cell is themost advanced candidate. U.S. Pat. No. 5,409,784 disclosesplasmatron/fuel cell combinations and the teachings of this patent areincorporated herein by reference.

[0012] The prior art also does not disclose the possible use ofwater/steam in the reforming process.

SUMMARY OF THE INVENTION

[0013] In one aspect, the plasmatron-catalyst system of the inventionfor generating hydrogen rich gas includes a plasmatron and at least onecatalyst for receiving an output from the plasmatron to produce hydrogenrich gas. The catalyst is located at such a position downstream from theplasmatron as to be activated by the hydrogen and radicals produced bythe plasmatron. In a preferred embodiment, the plasmatron receives as aninput air, fuel and water/steam. The plasmatron may also receive exhaustgas from an engine or fuel cell. It is preferred that the at least onecatalyst receive as an input air, fuel and water/steam. The catalyst mayalso receive exhaust gas from an engine or fuel cell.

[0014] In another embodiment, the at least one catalyst includes a heatexchanger in heat exchange relation with the catalyst to preheat theair, fuel and water/steam. One embodiment includes a plurality ofcatalyst sections wherein each catalyst section receives additional air,fuel or water/steam.

[0015] In another aspect, the plasmatron catalyst system furtherincludes a fuel cell for receiving the hydrogen rich gas, the hydrogenrich gas having reduced CO content. The fuel cell may be in a vehicle orin a stationary setting.

[0016] In another embodiment, the plasmatron is followed by fuelinjection system for a partial oxidation process, the fuel injectionsystem followed by a catalyst for improved yields, the catalyst followedby water/steam injection and a water-shift reformer catalyst wherebyhydrogen concentration is increased and CO concentration is decreased.In any of these embodiments, the catalyst may be a water-shiftingcatalyst. The catalyst may also be a partial oxidation catalyst or asteam reforming catalyst. In yet another embodiment, the catalysts are acombination of partial oxidation, steam reforming or water-shiftcatalyst with possible addition of water/steam in between adjacentcatalytic regions.

[0017] In another embodiment, the steam reforming catalyst is followedby a water-shifting catalyst, i with or without additional water/steaminjection prior to the water-shifting catalyst.

[0018] The present system may be operated in a less efficientnon-catalytic mode of operation during cold start followed thereafter bymore efficient catalytic plasma reforming after the catalyst reachesoperating temperature. The water/steam may be obtained from oxidation ofhydrogen in a fuel cell or by combustion in an engine such as a dieselengine. The water-steam may also be obtained from the exhaust of adiesel engine.

[0019] In yet another aspect, the hydrogen rich gas is delivered to acatalytic converter of an internal combustion engine wherein theenthalpy of the hydrogen-rich gas preheats and/or activates the catalystin the catalytic converter. The hydrogen-rich gas produced by the systemof the invention may also be used for reducing processes in metallurgyand chemistry. The hydrogen-rich gases may also be used forhydrogenation as in food processing and fuel upgrading.

[0020] In yet another embodiment, the CO content of the reformate isdecreased by the use of a non-thermal, catalytic reaction to selectivelyoxidize the CO to CO₂.

BRIEF DESCRIPTION OF THE DRAWING

[0021]FIG. 1. is a block diagram of an embodiment of the inventionillustrating multiple catalyst sections.

[0022]FIG. 2. is a block diagram of an embodiment of the inventionincluding a heat exchanger.

[0023]FIG. 3. is a block diagram of yet another embodiment of theinvention.

[0024]FIG. 4. is a block diagram of an embodiment of the inventionincluding a catalytic converter.

[0025]FIG. 5. is a block diagram of an embodiment of the inventionincluding a non-thermal plasma catalyst.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] Water/steam can be used to achieve several objectives in thereforming process. These objectives include use in a water-shiftreaction, downstream from the plasmatron and reactor, in order to reducethe CO concentration and increase the hydrogen concentration.Water/steam can also be used to perform steam reforming in which thewater/steam reacts with the hydrocarbon fuel to produce hydrogen and CO.Water/steam can also be used in an autothermal reaction in which bothair and water/steam are used in order to insure that the exothermicityof the partial oxidation process is balanced by the endothermicity ofthe steam reforming reaction. In this case, the reforming reaction isenergy neutral. The use of water/steam, oxygen and fuel in a plasmatronreactor forms a continuum of possibilities. In the case of partialoxidation, the maximum hydrogen yield is 100%, while when water/steam isadded the hydrogen yield can be larger than 100% by virtue of therelease of hydrogen from the water/steam.

[0027] It will be appreciated by those skilled in the art that exhaustgases, either from a fuel cell or an internal combustion engine may beused as an input to the plasmatron for reforming. In this case, thereformed gas composition is nitrogen, CO, CO₂, and water.

[0028] It has been demonstrated experimentally by the inventors herein,that by using catalysts downstream from the plasmatron, the electricalenergy consumption in the plasmatron is reduced substantially (by afactor of 9) with increased hydrogen yields (approaching 100%) and withrelatively small CO concentrations (at the present time, about 1-2%, butpossibly smaller in the future with improved reactor design).

[0029] The need to preheat the catalyst slows down the response of asystem operating in plasma catalysis mode. Fast response is needed,especially for on-board applications, for the fast generation ofhydrogen during initial operation of a vehicle after a prolonged shutdown. In order to allow for rapid response, the mode of operation of theplasmatron is varied. During cold starts, the plasmatron operates withlarger electrical input, resulting in gases with high enthalpy, thatallows for high yields without the need of the catalyst, but at theexpense of increased energy consumption. In other words, during coldstart the system operates in a non-catalytic mode. Once the catalystsare warmed up, the plasmatron energy input is decreased to the steadystate level allowed by the more efficient plasma catalyst.

[0030] The hydrogen rich gas from the plasmatron may also be introducedinto the catalytic converter that is used to control emissions from aninternal combustion engine. The hydrogen and radicals produced by theplasmatron interact with the catalyst, making it more active. Inaddition, combustion of the hydrogen rich gas on the catalytic surfaceincreases the temperature of the catalyst, and can be used for quickturn-on of catalyst during cold start-up. The long-lived radicalsproduced by the plasmatron also enhance the catalytic performance of theconverter.

[0031] The hydrogen productivity in plasma-catalytic mode, withwater/steam injection, can be very high, generating about 10 cubicmeters of hydrogen per liter of reactor.

[0032] There is a synergism between a plasmatron and a catalystdownstream from the plasmatron. Radicals produced in the plasma cantravel to the location of the catalyst and activate the catalyst. Inthis manner, very active catalysis can be generated. The very activecatalyst can be used as a means to: (1) increase the throughput throughthe catalyst (for constant volume catalyst, increased throughput andincreased space velocity through the catalyst); (2) decrease the amountof catalyst required, for a given flow rate; and (3) accomplish morethan one function of the catalyst, such as a combination of partialoxidation, steam reforming or water shifting, all within the samecatalyst, as space velocities that are greater than would be the case ifthere were no radical activation of the catalyst.

[0033] The catalyst needs to be close to the plasma, due to the finitelifetime of the relevant radicals and activated species. Their lifetimesare on the order of 10 microseconds to 1 millisecond. For velocities of10-100 m/s, the catalyst needs to be located within 1 cm to 10 cmdownstream from the plasma source in order to effectively use theradicals that are generated.

[0034] With reference now to FIG. 1, a plasmatron 10 is supplied withelectrical power 12. It is contemplated that this plasmatron will alsoreceive as input air 14, fuel 16, water 18 and optionally exhaust gas20. In this embodiment, the output of the plasmatron 10 passes into afirst catalyst section 22 and from there into a second catalyst section24. Any number of additional catalyst sections may be added up tocatalyst n illustrated at 26 in FIG. 1. The catalyst used in thecatalyst sections may be a water-shifting catalyst, a partial oxidationcatalyst or a steam reforming catalyst. The inputs of air 14, fuel 16,and water 18 can be introduced in controlled amounts, including justwater/steam. The catalyst or catalysts are located in a positiondownstream from the plasmatron so as to be activated by hydrogen andradicals produced by the plasmatron.

[0035] With reference to FIG. 2, a heat exchanger 28 is provided in heatexchange relation with a catalyst n (identified as 26). The heatexchanger 28 will preheat the air, fuel and water before it enters theplasmatron 10. Any number of additional catalysts may then follow. Asimilar arrangement is shown in FIG. 3 in which the heat exchanger 28serves to preheat fuel, air and water before it enters the firstcatalyst 22.

[0036] A very important aspect of the present invention is illustratedin FIG. 4. In this embodiment, the output of the plasma and the multiplecatalyst stages is directed to a catalytic converter 30 such asconventionally used with internal combustion engines. In this case, thehydrogen-rich gas and radicals produced by the plasmatron interact withthe catalyst making it more active. In addition, air and fuel may beinjected into the catalytic converter 30 so that combustion of thehydrogen-rich gas on the catalytic surface increases the temperature ofthe catalyst and can be used for quick turn-on of the catalyst duringcold start up. Additionally, one or more catalysts may also bepositioned within or as part of the catalytic converter 30.

[0037] Finally, with reference to FIG. 5, the output of theplasmatron-catalyst system is introduced into a non-thermal plasmacatalyst of 32 which produces a hydrogen-rich gas with a low CO content.

[0038] With reference again to FIG. 1, those skilled in the art willrecognize that hydrogen rich gas from the last catalyst stage may bedelivered to an engine or fuel cell 34.

[0039] It is thus seen that the present invention results in a rapidresponse plasmatron/catalyst system which can maximize the hydrogenyield and decrease the amount of carbon monoxide by using water/steam inthe reforming process.

[0040] It is recognized that modifications and variations of the presentinvention will occur to those skilled in the art and it is intended thatall such modifications and variations be included within the scope ofthe pended claims.

What is claimed is:
 1. Plasmatron-catalyst apparatus for generatinghydrogen-rich gas comprising: a plasmatron; and at least one catalystfor receiving an output from the plasmatron to produce hydrogen-richgas, wherein said at least one catalyst is located at a positiondownstream from the plasmatron so as to be activated by hydrogen andradicals produced by the plasmatron.
 2. The apparatus of claim 1 whereinthe plasmatron includes means for receiving as an input air, fuel andwater/steam.
 3. The apparatus of claim 2 wherein the plasmatron includesmeans for receiving exhaust gas from an engine or fuel cell.
 4. Theapparatus of claim 1 wherein the at least one catalyst includes meansfor receiving as an input air, fuel and water/steam.
 5. The apparatus ofclaim 4 wherein the at least one catalyst includes means for receivingexhaust gas from an engine or fuel cell.
 6. The apparatus of claim 2wherein the at least one catalyst includes a heat exchanger in heatexchange relation with the catalyst to preheat the air, fuel andwater/steam.
 7. The apparatus of claim 1 including a plurality ofcatalyst sections, wherein each catalyst section receives additionalair/fuel or water/steam.
 8. The apparatus of claim 1 further including afuel cell for receiving the hydrogen-rich gas, the hydrogen-rich gashaving reduced CO content.
 9. The apparatus of claim 8 wherein theplasmatron-catalyst apparatus is in a vehicle.
 10. The apparatus ofclaim 8 wherein the plasmatron-catalytic system is stationary.
 11. Theapparatus of claim 1 wherein the plasmatron is followed by a fuelinjection system for a partial oxidation process, the fuel injectionsystem followed by said at least one catalyst, said at least onecatalyst followed by means for water/steam injection and awater-shifting catalyst whereby hydrogen concentration is increased andCO concentration is decreased.
 12. The apparatus of any of claims 1-11wherein said at least one catalyst is selected from the group consistingof a water-shifting catalyst, a partial oxidation catalyst and a steamreforming catalyst.
 13. The apparatus of claim 11 wherein said at leastone catalyst is a combination of a partial oxidation catalyst, a steamreforming catalyst and a water-shifting catalyst.
 14. The apparatus ofclaim 13 wherein the steam reforming catalyst is followed by thewater-shifting catalyst with additional water/steam injection prior tothe water-shifting catalyst.
 15. The apparatus of claim 2 wherein thewater/steam is obtained from oxidizing hydrogen in a fuel cell or bycombustion in an engine.
 16. The apparatus of claim 15 wherein saidcombustion in an engine includes combustion in a diesel engine.
 17. Theapparatus of claim 2 wherein the water/steam is obtained from theexhaust from a diesel engine.
 18. The apparatus of claim 1 wherein thehydrogen-rich gas is used for reduction processes in metallurgy andchemistry.
 19. The apparatus of claim 1 wherein the hydrogen-rich gas isused for hydrogenation as in food processing and fuel upgrading.
 20. Theapparatus of claim 1 further including a non-thermal catalytic reactionelement to selectively oxidize CO to CO₂.
 21. The apparatus of claim 11wherein said at least one catalyst is a combination of a partialoxidation catalyst, a steam reforming catalyst, and a water-shiftingcatalyst, wherein water/steam is added between each of the catalysts.22. The apparatus of claim 13 wherein the steam reforming catalyst isfollowed by the water-shifting catalyst without additional water/steaminjection prior to the water-shifting catalyst.
 23. The apparatus ofclaim 1 further including an engine wherein said hydrogen rich gasgenerated by said plasmatron-catalyst apparatus is delivered to saidengine.
 24. The apparatus of claim 1 wherein said position of the atleast one catalyst is within 1 to 10 cm downstream from the plasmatron.25. Plasmatron-catalyst apparatus for generating hydrogen-rich gascomprising: a plasmatron; and a catalytic converter containing at leastone catalyst for receiving an output from the plasmatron to producehydrogen-rich gas, wherein said at least one catalyst in said catalyticconverter is located at a position downstream from the plasmatron and isactivated by hydrogen and radicals produced in the output of theplasmatron.
 26. The apparatus of claim 25 wherein said at least catalystin said catalytic converter is further activated and/or preheated by theenthalpy of the output of the plasmatron.
 27. The apparatus of claim 25wherein said plasmatron-catalyst apparatus operates in conjunction withan internal combustion engine.
 28. The apparatus of claim 25 wherein theplasmatron-catalyst apparatus is in a vehicle.
 29. The apparatus ofclaim 25 wherein said position of the at least one catalyst is within 1to 10 cm downstream from the plasmatron.